The invention relates generally to the field of support devices, and more particularly, pertains to support arms for electronic devices, such as a computer monitor, flat screen display, television, or keyboard which are adjustable to a variety of positions and have a counterbalance to support the weight of the electronic device.
Positionable support arms for mounting electronic peripheral devices, such as computer monitors or televisions to, among other things, a wall, column, ceiling, desktop or other support structure are well known in the prior art. Conventional support arms include a rigid elongated arm having a first end pivotally coupled to the support structure for pivoting movement about a generally horizontal first pivot axis and vertically between and upper and lower position. A mounting element is provided for coupling a device to a second end of the rigid arm, which typically provides for pivoting of the device about a second generally horizontal pivot point, and vertically to maintain the orientation of the device as the arm is moved between upper and lower positions.
Some conventional support arm systems rely on frictional contact between moving parts of the rigid arm to hold a device in the desired position relative to the support structure. Such systems require that the frictional forces overcome the force of gravity acting on the support arm and the associated device. For example the arm may include a frictional assembly at a pivot point including at least two planar surfaces where a nut, bolt and spring washer assembly provide tension to the assembly.
Other conventional support arms of the prior art include conventional springs, gas springs, also referred to as gas cylinders or pneumatic cylinders, or other biasing means to counterbalance at least a portion of the weight supported by the support arm. See, for example, U.S. Pat. No. 6,409,134 to Oddsen, Jr., commonly assigned, which describes an extension arm for mounting an electronic peripheral device which utilizes a gas spring. Similarly, U.S. Pat. No. 6,076,785 to Oddsen, Jr., also commonly assigned, describes an adjustable keyboard support which is maintained in position by a pneumatic cylinder. Both of these references are incorporated herein by reference.
For further illustration, FIG. 1 is a drawing of an assembled support arm 500 for mounting a peripheral device in accordance with the prior art. As depicted, the main elements of the support arm 500 are a first endcap 502, an upper channel 504, a lower channel 506, a second endcap 508, and a gas spring 510. The first endcap 502 has an endcap shaft 512 that is pivotally attachable to a rigid support mount (not shown), such as an orifice sized to accept the endcap shaft 512 or a track configured and sized to engage the grooves on endcap shaft 512. The rigid support mount is in turn secured to a support structure (not shown). The first endcap 512 is pivotally coupled via pins 514 to both the upper channel 504 and lower channel 506. The opposite ends of upper channel 504 and lower channel 506 are pivotally coupled via pins 516 to the second endcap 508. The second endcap is coupled to a mounting element (not shown) for holding a device (not shown) such as an electronic peripheral device. The combination of the upper and the lower channels 504,506 and the first and the second endcaps 502,508 form an adjustable parallelogram that permits a device coupled to the mounting element to be raised and lowered to a desired height. The parallelogram retains its position by employing a gas spring 510 which is pivotally and adjustably attached to the first endcap 502 and an outward portion of the upper channel 504 as further described below. Thus, the gas spring 510 causes the parallelogram to retain its position when the only force exerted on the support arm 500 is the weight of the support arm coupled with the weight of the supported device, but permits the parallelogram to be adjusted when a user applies downward or upward force to the endcap 508.
One end of the gas spring 510 is attached to an outward portion of upper channel 504 as shown. A hole disposed at one end of the upper channel has a threaded ball stud 534 placed within the hole and secured by a nut 536. The ball stud 534 is adapted to receive one end of the gas spring 510 via attachment 538 to form a ball and socket joint.
Disposed within the first endcap 502 is a threaded rod 518 which is inserted in a hole (not shown) at the base of endcap 502, and secured in place by a clip 520. The clip is fastened to an inner surface of the first endcap 502 by screws 522. Threadedly mounted on the threaded rod 518 is a clevis 522 threaded through a centrally located tapped hole (not shown). At a first end of the clevis 522 is a pair of fastening members 524 to which are fastened one end of the gas spring 510 by attachment 526. A second end of the clevis 522 is configured to slidably engage a track 528 which is integrally molded in the first endcap 502. A first end 530 of the threaded rod 518 is configured to be engaged by a hex-shaped key (not shown) which is inserted through hole 532 at the top of endcap 502 when first end 530 of the threaded rod 518 is properly aligned with hole 532. The hex-shaped key is employed so as to rotate the threaded rod 518. When the threaded rod 518 is rotated, the clevis moves along the length of the threaded rod in a direction corresponding to the direction the key is tuned. This movement of the clevis permits the gas spring to be adjusted.
Support arms employing gas springs, such as the one shown in FIG. 1 and others like it, are considerably more expensive than support arms which rely upon frictional resistance as a basis for maintaining the position of the arm and supporting the weight of the device. They typically require an adjustment mechanism such as that described above, which means they are more costly to manufacture and difficult to assemble. Further, gas springs tend produce a bouncing movement when they are moved, which is particularly undesirable when the support arm is used in connection with a support for a keyboard, wherein the typing produces repeated downward motion but the user desires the keyboard to remain in a fixed position. Friction based devices, on the other hand, are often limited in the amount of weight they can support, and are typically difficult to adjust. Ordinarily, friction based supports are locked in a fixed position. Moreover, such devices tend to be unreliable, and are thus not as desirable for use with expensive and delicate electronic equipment.
Accordingly, notwithstanding the existence of support arms including a gas spring, there is a need for a reliable friction-based support arm that is easy to assemble and adjust, and that is less expensive to manufacture than conventional support arms including a gas spring.